Unit 3

• Energy


  Capacity to do work
• Types of energy work

  • Chemical work (making & breaking of chemical bonds)
  • Transport work (moving ions, molecules & larger particles, can create concentration gradients)
  • Mechanical work (used for movement)
• Laws of thermodynamics


  • 1st law: total amount of energy in the universe is constant (law of conservation of energy)
  • 2nd law: the total entropy of an isolated system will always increase over time
• Kinetic energy


  Energy of motion
• Potential energy


  Stored energy
• Activation energy


  Minimum amount of energy required for a chemical reaction to occur

  
• Chemical reactions


  1. Reactants

  2. Activation of reaction

  3. Reaction process

  4. Products
• Exergonic reactions


  Reversible reactions with large & negative net free energy change
• Endergonic reactions


  Irreversible reactions with small & positive net free energy change
• Metabolism


  Sum of all chemical reactions in the body
• Anabolism


  Building small molecules into larger ones, requires energy
• Catabolism


  Breakdown of larger/complex molecules into simpler ones, releasing energy

  
• Enzymes


  • Complex biomolecules, typically globular proteins, that catalyse chemical reactions
  • Highly specific to particular substrate
  • Not consumed in reactions, so are used repeatedly

  
• Induced-fit model of enzyme function

  Enzymes accelerate chemical reactions by lowering activation energy

  
• Alcohol dehydrogenase, an enzyme found in the stomach and liver, removes ethanol from the body by oxidizing it to acetaldehyde. Zinc is a cofactor for alcohol dehydrogenase. If a person's intake of zinc were deficient, this would affect the activity of alcohol dehydrogenase and the person's ability to tolerate alcohol.
• Types of enzymatic reactions

  • Activation of enzymes (increase activity through binding of cofactor, coenzyme or change in pH or temperature)
  • Inactivation (decreasing/stopping activity)
  • Modulation (changing activity level in response to signals e.g feedback inhibition)

  
• Feedback inhibition


  The product of the pathway inhibits its own production by competitively inhibiting the binding of a substrate to the active site of an enzyme within the metabolic pathway

  
• ATP


  Energy currency of the cell (adenosine triphosphate)

  
• ATP production


  1. Aerobic pathway (require oxygen, produce most of the ATP)

  2. Anaerobic pathway (no oxygen required, produce small amounts of ATP)

  
• Electron Transport Chain


  1. High-energy electrons from glycolysis

  2. Energy released during metabolism is captured by high-energy electrons carried by NADH and FADH2

  3. Energy from high-energy electrons moving along the electron transport system pumps H+ from the matrix into the intermembrane space

  4. Electrons at the end of the electron transport system are back to their normal energy state, they combine with H+ and oxygen to form water

  5. Potential energy captured in the H+ concentration gradient is converted to kinetic energy when H+ ions pass through the ATP synthase, some of the kinetic energy is captured as ATP
• Lipid metabolism


  1. Lipases digest triglycerides into glycerol and 3 fatty acids

  2. Glycerol becomes a glycolysis substrate

  3. β-oxidation chops 2-carbon acyl units off the fatty acids, acyl units become acetyl CoA and can be used in the citric acid cycle

  
• Protein metabolism


  Catabolism of proteins, carbohydrates, and fats
• Pyruvate dehydrogenase complex (PDC) deficiency is a genetic disorder that affects pyruvate dehydrogenase complex, causing low levels of PDC which decreases the total amount of energy produced by cells, leading to developmental defects, muscle spasms, and death.
• Phenylketonuria (PKU) is a genetic disorder that affects the way the body processes the amino acid phenylalanine, caused by a deficiency or dysfunction of the enzyme phenylalanine hydroxylase, leading to a build up of phenylalanine that causes mental retardation.
• Energy


  Capacity to do work
• Types of energy


  • Chemical work
  • Transport work
  • Mechanical work
• Laws of thermodynamics


  • 1st law: total amount of energy in the universe is constant (law of conservation of energy)
  • 2nd law: the total entropy of an isolated system will always increase over time
• Kinetic energy


  Energy of motion
• Potential energy


  Stored energy
• Activation energy


  Minimum amount of energy required for a chemical reaction to occur
• Chemical reactions


  1. Activation of reaction

  2. Reaction process

  3. Products
• Exergonic reactions


  Net free energy change is large and negative
• Endergonic reactions


  Net free energy change is small and positive
• Metabolism


  Sum of all chemical reactions in the body
• Anabolism


  Small molecules built into larger ones; requires energy

  
• Catabolism


  Breakdown of larger/complex molecules into simpler ones releasing energy

  
• Enzymes


  • Complex biomolecules, typically globular proteins, that catalyse chemical reactions
  • Highly specific to particular substrate
  • Not consumed in reactions, so are used repeatedly

  
• Induced-fit model of enzyme function

  Reactants (A+B) = substrates

  
• Alcohol dehydrogenase, an enzyme found in the stomach and liver, removes ethanol from the body by oxidizing it to acetaldehyde. Zinc is a cofactor for alcohol dehydrogenase. If a person's intake of zinc were deficient, how would this deficiency affect the activity of alcohol dehydrogenase and the person's ability to tolerate alcohol?
• Types of enzymatic reactions

  • Activation of enzymes
  • Inactivation
  • Modulation